Prevalence of attention deficit hyperactivity disorder in schoolchildren in Athens, Greece. Association of ADHD subtypes with social and academic impairment.

The aim of this study was to explore the prevalence of attention deficit hyperactivity disorder (ADHD) and social and academic impairment in 6- to 11-year-old children residents of Athens, Greece. We screened 603 elementary schoolchildren following grades first to sixth. A two-stage screening process was employed including a standardized ADHD test for teachers and the Teacher Report Form (TRF). Among the 603 children, 36 (6.0%) met the study criteria for ADHD. The estimated prevalence was 8% for boys and 3.8% for girls. The most prevalent subtype of ADHD was the combined type (3.8%), followed by the ADHD inattentive (1.7%) and the ADHD hyperactive-impulsive type (0.5%). The ADHD-combined type was strongly associated with clinical impairment in both areas of functioning (academic and social), where the ADHD inattentive subtype was found to be strongly associated with academic problems. The ADHD hyperactive-impulsive type was the less prevalent and the less impaired subtype in this study. None of the 36 children had been previously diagnosed as having ADHD or other primary disorder. In conclusion, the prevalence of ADHD among schoolchildren in Athens and the risk factors were found to be comparable to those reported in other countries worldwide. Additionally, impairment in social and academic functioning was strongly associated with the subtypes of the disorder.

Properties and potential of bone marrow mesenchymal stromal cells from children with hematologic diseases.

BACKGROUND: Mesenchymal stromal cells (MSC) have become the focus of cellular therapeutics but little is known regarding bone marrow (BM) MSC derived from children. As MSC constitute part of BM stroma, we examined their properties in children with hematologic diseases. METHODS: BM MSC from children with non-malignant hematologic disorders and acute lymphoblastic leukemia (ALL) were isolated and expanded. MSC were immunophenotypically characterized and their functional characteristics were assessed by CFU-F assay and cell doubling time calculation. Their ability for trilineage differentiation was verified by molecular and histochemical methods. Apoptosis was evaluated and clonal analysis was performed. RESULTS: MSC were isolated from BM of all groups. They acquired the mesenchymal-related markers from the first passage, with a simultaneous decrease of hematopoietic markers. A very low percentage of apoptotic cells was detected in all passages. The proliferative and clonogenic capacity did not differ among groups, with the exception of ALL at diagnosis, in which they were defective. Histochemical and molecular analysis of differentiated MSC yielded characteristics for adipocytes, osteoblasts and chondrocytes. Clonal analysis in a number of BM samples revealed a highly heterogeneous population of cells within each clone. DISCUSSION: MSC from BM of children with hematologic disorders, with the exception of ALL at diagnosis, can be isolated in sufficient number and quality to serve as a potential source for clinical applications.

Quantitative assessment of PRAME expression in diagnosis of childhood acute leukemia.

PRAME is expressed at low levels in normal testes and highly in solid tumor cells and hematological malignancies. The purpose of this study was to investigate PRAME expression levels in children with acute leukemia with real-time PCR analysis. Seventeen children with newly diagnosed or relapsed acute leukemia (11 ALL, 4 AML, 1 acute myeloblastic leukemia secondary to MDS, 1 ALL at relapse) and a control group of seven children were studied. Overexpression of PRAME was found in 52.9% (3 AML, 6 ALL) of the patients studied. No important correlation between PRAME expression and the patients' prognosis was observed. The above findings indicate that PRAME expression in acute leukemia does not seem to be of prognostic significance, whereas it might represent a candidate marker for the monitoring of minimal residual disease.

Quantitative assessment of WT1 expression in diagnosis of childhood acute leukemia.

The purpose of this study was to investigate WT1 expression levels in childhood acute leukemia. Bone marrow from 14 children with acute leukemia at diagnosis and from 7 children with solid tumors without bone marrow involvement (control group) was studied. Five of the 14 patients (35.7%), expressed high levels of WT1. Four of the five WT1 positive patients with additional adverse prognostic factors, have succumbed to their disease. The results of this study are in accordance with the fact that high levels of WT1 expression have been reported in patients with an unfavorable outcome.

Macrophages orchestrate the immune response to tumor cell death.

The mechanisms by which the immune system distinguishes normal developmental cell death from pathological immunogenic cell killing are central to effective cancer immunotherapy. Using HSVtk suicide gene therapy, we showed that macrophages can distinguish between tumor cells dying through classical apoptosis and tumor cells engineered to die through nonapoptotic mechanisms, resulting in secretion of either immunosuppressive cytokines (interleukin 10 and transforming growth factor beta) or inflammatory cytokines (tumor necrosis factor alpha or interleukin 1beta), respectively. Additionally heat shock protein 70 acts as one component of a bimodal alarm signal that activates macrophages in the presence of stressful, immunogenic tumor cell killing. These differential responses of macrophages can also be used to vaccinate mice against tumor challenge, using adoptive transfer, as well as to cure mice of established tumors.

Transcriptional control: an essential component of cancer gene therapy strategies?

The therapeutic index of cancer gene therapy approaches will, at least in part, be dictated by the spatial and temporal control of expression of the therapeutic transgenes. Strategies which allow precise control of gene transcription are likely to play a crucial role in the future pre-clinical and clinical development of gene therapy. In this review, we discuss these issues as they relate to tissue and tumor specific promoters. In addition, the exciting opportunities offered by the development of regulated gene expression systems using small molecules, radiation and heat are reviewed. It is realistic to expect that the future offers the prospect of amalgamating elements of a number of these different systems in a co-ordinated gene delivery approach with the potential to increase the efficacy and reduce the toxicity of treatment.

Heat shock protein 70 induced during tumor cell killing induces Th1 cytokines and targets immature dendritic cell precursors to enhance antigen uptake.

Previously, we reported that killing tumor cells in vivo with the HSV thymidine kinase/ganciclovir system generates potent antitumor immunity, determined in part by the mechanism by which the cells die and by the levels of inducible heat shock protein (hsp) expression induced during the process of cell death. Here, we show that induction of hsp70 expression induces an infiltrate of T cells, macrophages, and predominantly dendritic cells (DCs) into the tumors as well as an intratumoral profile of Th1 cytokine expression (IFN-gamma, TNF-alpha, and IL-12) and enhances immunogenicity via a T cell-mediated mechanism. In addition, the protection conferred by hsp70 is both tumor and cell specific. We also demonstrate that hsp70 targets immature APC to make them significantly more able to capture Ags. This is likely to optimize cross-priming of the infiltrating APC with tumor Ags, which are simultaneously being released by the dying cells. In addition, using an Myc epitope-tagged hsp70 expression vector, we present evidence that hsp70 released from dying tumor cells is taken up directly into DCs and may, therefore, be involved in direct chaperoning of Ags into DCs. Taken together, our data suggest that hsp70 induction serves to signal the immune system of the presence of an immunologically relevant (dangerous) situation against which an immune reaction should be raised.